Difficulty epoch
Mining & BlocksThis term is part of the Bitcoin glossary — See all terms
A difficulty epoch is the ~2-week, 2,016-block window between difficulty adjustments — like a school term after which grades get recalculated.
Bitcoin's clock works in epochs of 2,016 blocks. During an epoch the difficulty stays fixed; at the end, the network measures how long the epoch took and sets a new difficulty for the next one. An epoch should last exactly two weeks at the 10-minute target, but in reality ranges from a few days (when hashrate explodes) to over a month (when miners flee).
You can see the current epoch in real time on this site: the countdown card shows the epoch number, how far along it is, and the estimated date of the next retarget. Epochs are also how people count Bitcoin's mining history — epoch 481, for example, is the one we're living in today.
